Demining device including demining discs and impact devices and demining method utilizing the device

ABSTRACT

A method for increasing effectiveness of mine clearance when clearing landmines. A vehicle-mounted, mechanically driven, rotary cultivator type demining tool is provided. The demining tool includes a horizontal shaft, a demining unit rotating around the horizontal shaft, a plurality of parallel demining discs located at a distance from each other and rotating around the shaft which when the demining tool is in operation cut down into an upper ground layer to a pre-determined depth to cause mines in their path to detonate or to fragment into harmless fragments, and impact devices located between the demining discs for working the upper ground layer between the demining discs such that the impact devices impact with the upper ground layer between each pair of demining discs several times per rotation of the demining tool. An upper ground layer where mines may be deployed is worked with the demining tool.

FIELD OF THE INVENTION

The present invention relates to a method and a device for rapidclearance of landmines lying freely on the surface or buried in theupper ground layer, including both small anti-personnel (AP) mines andlarger anti-vehicle and anti-tank mines.

BACKGROUND OF THE INVENTION

For rapid clearance of routes through minefields the military havepreviously used primarily chain flails and mine ploughs. Theses are mostappropriate for military purposes and have achieved far from the 100%clearance result that is desirable in civil mine clearance operationsafter a conflict is over. Civil mine clearing operations have thus beenachieved by the time consuming and labor intensive method of usingprobes or, perhaps, mainly by the use of electromagnetic mine detectors.The latter are, in fact, very sensitive but there are AP mines that donot contain any metal at all and are thus not detected. Moreover, thenumber of false indications that have to be checked is always high,especially in areas where battles have occurred as there is always amultitude of fragments in the ground in such areas.

In latter years, however, increasing interest has been focused onmechanical mine clearance vehicles that operate in a similar way to themechanical rotary cultivator principle. They have been shown to havegood capacity, and although they cannot operate in all types of terrainthey clearly constitute a positive addition to the field of mineclearing.

Many of these rotary cultivator type demining tools are designed withhorizontal rotation shafts fitted with multi-disc cultivators, each discusually being fitted with individual teeth around its periphery.

The basic concept for the rotary cultivator disc type of mine clearingdevice is described in WO 95/24604, while DE 4.442.135 describes avariant of the same basic concept in which the various discs incorporatevery large teeth machined direct in the actual disc and with aperturesto reduce the risk of damage in the event of mine detonations in orunder the demining tool.

The objective with demining tools that function on the rotary cultivatorprinciple is that they shall ‘chew’ the mines in their path into smallfragments or cause the mines to detonate. In practice it has been shownthat usually mines are made to detonate in or under the demining toolwhich is usually no problem in the case of AP mines, but anti-vehicleand anti-tank mines easily cause damage to the demining tool.Consequently, it should be easy to repair or replace.

In practice, however, the main problem with demining tools of the aboverotary cultivator type has not been damage to the demining tool by minedetonations initiated, but that individual mines—especially small APmines—can pass undamaged through the demining tool. Quite simply, it hasbeen difficult to achieve the virtual 100% mine clearance effectnecessary in civil mine clearing. The cultivator discs cannot be locatedtoo densely as the closer they are to each other the higher the machinepower that is needed.

SUMMARY OF THE INVENTION

The objective of the present invention is to raise the clearancepercentage of demining tools of the above mentioned basic type.

As a demining tool of the above rotary disc roller type works, the upperground layer down to a predetermined depth the soil worked collectsbetween the cultivator discs and this accumulated soil sometimesincludes undamaged individual mines.

We have now—significantly—found that mines embedded in this accumulatedsoil between the cultivator discs can be made to detonate if we mount anumber of impact devices in the form of impact segments between thecultivator discs. These impact segments co-rotate with the shaft of therotary cultivator discs and are arranged in a plane parallel with thecultivator discs with several impact segments in one and the same planewith a space between each impact segment so that as impact segments inthe same plane follow each other (in rotation) they work the accumulatedsoil between the cultivator discs. The number of such impact devices ineach plane may be 2-10, but preferably 5-10. In the preferred designthey also have a leading edge relative to their direction of rotationthat is bevelled rearwards in the direction of rotation of the rollersuch that the section of the impact segment closest to the axis ofrotation first meets the accumulated soil between the cultivator discsand the leading edge of each impact segment has a sawtooth form.

The design of the leading edge of each impact segment and the spacebetween each impact segment in the same rotational plane results inworking of the accumulated soil between each two adjacent cultivatordiscs while the intermittent agitation of the accumulated soil by theimpact devices acts to trigger all types of pressure sensitive AP mines.

Practical tests with live mines in completely realistic conditions haveshown that by supplementing an otherwise equivalent demining tool withthe impact devices claimed in the present invention, the mine clearancecapability is increased from approximately 95% to 99%.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention shall now be described in more detail withreference to the appended figures:

FIG. 1 shows a perspective view of a demining vehicle, while

FIG. 2 shows the design principle of the demining tool, and

FIG. 3 shows a detailed illustration of one of the impact devices asclaimed in the present invention, and

FIGS. 4 & 5 show different mechanical attachments for the impactdevices.

DETAILED DESCRIPTION OF THE INVENTION

The main parts of the demining vehicle 1 illustrated in FIG. 1 are thechassis 2, the engine unit 3, control cab 4, drive tracks 5 and 6, andthe actual demining tool 7. The latter comprises a roller-shaped shaft 8fitted with a number of parallel demining discs 9, each of which isfitted with peripheral teeth 10 made of a hard material to minimise wearround the periphery of the demining discs 9. The demining tool 7 isjournalled to enable rotation in an inverted cradle 11 which in turn canbe raised or lowered to enable different operating depths in the upperground layer. The engine 3 is used to drive both the demining vehicle 1and to rotate the demining tool 7. The demining tool 7 illustrated inFIG. 1 is of a more general nature and is not designed in accordancewith the present invention.

The demining tool 12 in FIG. 2 is shown in more detail to illustrate thedesign as claimed in the present invention. It consists of a centraltubular roller shaft 13, a number of demining discs 14. Although only afew discs are illustrated in the figure, each one incorporates a numberof fingers around its periphery and generally designated 15. Each fingeris free on three faces (around the axis of rotation). Also each fingercan be fitted with a tooth holder of the type vaguely indicated on FIG.1. The tooth holder can in turn be fitted with a tooth made of hardmaterial. To provide these demining discs 14 with the optimal operatingcharacteristics, the fingers at the periphery are angled outwards inopposite directions and at varying angles from the main plane of thedemining discs so that they form a zigzag pattern around the deminingdiscs. The actual angles cannot be specified generally but must betested and tried.

The impact devices 16 as claimed in the present invention, the design ofwhich is shown in more detail in FIG. 3, are mounted between each twoadjacent demining discs 14. The impact devices 16 are mounted betweenthe demining discs 14 with a certain distance between them.

The number of impact devices at each station on the roller, i.e. withineach space between two adjacent demining discs, is 2-10 and preferably5-10. They can be mutually aligned or be slightly displaced laterally inrelation to each other. Between each two impact devices there is alwaysa large or small space. The impact devices 16 incorporate anoblique—relative to the main direction of operation of the demining tool12—leading edge which, one-after-one, strike the accumulated soil thatthey are designed to demine further and further outwards from therotational axis of the demining tool 12. The main direction of operationis designated A on FIGS. 3 and 5. To enhance their effectiveness eachimpact device also has a sawtooth shaped leading edge as illustrated inthe figures. Each sawtooth comprises a longitudinal edge 17, which onlyslightly deviates from the main direction of the leading edge of theimpact device 16, and a short lateral edge 18 that cuts mainly rightthrough the main direction of the leading edge of the impact device 16.

In the general type of demining tool 12 illustrated in FIG. 2 with acentral roller it is desirable to restrict the number of welded jointsto a minimum. However, it is difficult to avoid welding the deminingdiscs to the roller. On the other hand, it is possible to attach theimpact devices mechanically.

FIG. 4 illustrates part of a longitudinal projection of a demining toolof the type as claimed in the present invention in which 17 denotes theroller shaft, 18, 19 and 20 denote the demining discs, and 21 and 22signify two impact devices. The latter are welded onto holders 23 and 24which are in turn attached to each side of the demining discs by bolts25-27.

Another variant of mechanical attachment of the impact devices is shownin FIG. 5 in the form of a cross-section through a demining toolillustrating the central roller shaft 28, a demining disc 29, and twosemi-circular attachment devices 30 and 31 with lugs 32-35 assembled andheld together by bolts 36 and 37, and showing some of the impact devices38 welded to each of the attachment devices 30, 31.

What is claimed is:
 1. A method for increasing effectiveness of mineclearance when clearing landmines, comprising: providing avehicle-mounted, mechanically driven, rotary cultivator type deminingtool comprising a horizontal shaft, a demining unit rotating around thehorizontal shaft, a plurality of parallel demining discs located at adistance from each other and rotating around the shaft which when thedemining tool is in operation cut down into an upper ground layer to apre-determined depth to cause mines in their path to detonate or tofragment into harmless fragments, and impact devices located between thedemining discs for working the upper ground layer between the deminingdiscs such that the impact devices impact with the upper ground layerbetween each pair of demining discs several times per rotation of thedemining tool; and working an upper ground layer where mines may bedeployed with the demining tool.
 2. The method according to claim 1,further comprising: providing the demining discs with circular toothedouter peripheries.
 3. A vehicle-mounted demining tool for clearinglandmines by working an upper ground layer where mines may be deployed,the device comprising: a horizontal roller shaft; a plurality ofparallel demining discs arranged on the roller shaft a distance fronteach other and rotating with the roller shaft and which as the deminingtool operates cut down into the upper ground layer to a pre-determineddepth to cause mines in their path to detonate or to be fragmented intoharmless fragments; and radially projecting impact devices arranged onthe roller shaft in spaces between each two adjacent demining discs, theimpact devices working the upper ground layer between the deminingdiscs.
 4. The device according to claim 3, wherein the impact devicesrotate several times per rotation of the demining tool.
 5. The deviceaccording to claim 3, wherein the demining discs comprise circulartoothed outer peripheries.
 6. The device according to claim 3, whereinthe impact devices are fixed.
 7. The device according to claim 3,wherein the device operates as a rotary cultivator.
 8. The deviceaccording to claim 3, wherein each impact device comprises an obliqueleading edge in a direction of impact relative to the upper ground layerwith which it impacts such that a section of the impact device closestto an axis of rotating of the demining tool impacts with the upperground layer first.
 9. The device according to claim 8, wherein theoblique edge comprises sawtoothed notches.
 10. The device according toclaim 9, wherein each of the sawtoothed notches comprises an elongatedlongitudinal edge in a main direction of the oblique edge and a shortlateral edge substantially at a right angle to the longitudinal edge.11. The device according to claim 3, wherein the number of impactdevices between each pair of demining discs is 2-10.
 12. The deviceaccording to claim 11, wherein there is a free space between eachadjacent impact devices in the same radial plane.
 13. The deviceaccording to claim 3, wherein the number of impact devices between eachpair of demining discs is 5-10.
 14. The device according to claim 13,wherein there is a free space between each adjacent impact devices inthe same radical plane.
 15. The device according to claim 3, furthercomprising: holders for attaching the impact devices to the deminingdiscs located on either side of impact devices.
 16. The device accordingto claim 3, further comprising: holders attached in or around the rollershaft for attaching the impact devices.
 17. The device according toclaim 3, wherein the demining discs mounted on the roller shaft bywelding.
 18. The device according to claim 3, wherein each demining disccomprises a plurality of fingers arranged about a periphery of eachdemining disc, each finger comprising three free faces.
 19. The deviceaccording to claim 18, further comprising: at least one tooth holder oneach finger, each tooth holder incorporating a tooth made of hardmaterial.
 20. The device according to claim 18, wherein the fingers arecut out of the demining discs.
 21. The device according to claim 18,wherein each finger is angled out relative to a main plane of thedemining disc.
 22. The device according to claim 21, wherein each fingeris angled out at opposite angle from an adjacent finger.
 23. The deviceaccording to claim 18, wherein each finger is fitted with a toothconstructed of a hard material.